/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/

/*
 *  DTLS cookie callbacks implementation
 *
 *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  This file is part of mbed TLS (https://tls.mbed.org)
 */
/*
 * These session callbacks use a simple chained list
 * to store and retrieve the session information.
 */

#include "tls/config.h"

#if defined(MBEDTLS_SSL_COOKIE_C)

#include "tls/ssl_cookie.h"
#include "tls/ssl_internal.h"

#if defined(MBEDTLS_PLATFORM_C)
#include "tls/platform.h"
#else
#define mbedtls_calloc    calloc
#define mbedtls_free      free
#endif

#include "tls/ssl_cookie.h"
#include "tls/ssl_internal.h"

#include <string.h>

/* Implementation that should never be optimized out by the compiler */
static void mbedtls_zeroize(void *v, size_t n)
{
	volatile unsigned char *p = v;
	while (n--) {
		*p++ = 0;
	}
}

/*
 * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is
 * available. Try SHA-256 first, 512 wastes resources since we need to stay
 * with max 32 bytes of cookie for DTLS 1.0
 */
#if defined(MBEDTLS_SHA256_C)
#define COOKIE_MD           MBEDTLS_MD_SHA224
#define COOKIE_MD_OUTLEN    32
#define COOKIE_HMAC_LEN     28
#elif defined(MBEDTLS_SHA512_C)
#define COOKIE_MD           MBEDTLS_MD_SHA384
#define COOKIE_MD_OUTLEN    48
#define COOKIE_HMAC_LEN     28
#elif defined(MBEDTLS_SHA1_C)
#define COOKIE_MD           MBEDTLS_MD_SHA1
#define COOKIE_MD_OUTLEN    20
#define COOKIE_HMAC_LEN     20
#else
#error "DTLS hello verify needs SHA-1 or SHA-2"
#endif

/*
 * Cookies are formed of a 4-bytes timestamp (or serial number) and
 * an HMAC of timestemp and client ID.
 */
#define COOKIE_LEN      (4 + COOKIE_HMAC_LEN)

void mbedtls_ssl_cookie_init(mbedtls_ssl_cookie_ctx *ctx)
{
	mbedtls_zeroize(&ctx->mutex, sizeof(mbedtls_threading_mutex_t));

	mbedtls_md_init(&ctx->hmac_ctx);
#if !defined(MBEDTLS_HAVE_TIME)
	ctx->serial = 0;
#endif
	ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;

#if defined(MBEDTLS_THREADING_C)
	mbedtls_mutex_init(&ctx->mutex);
#endif
}

void mbedtls_ssl_cookie_set_timeout(mbedtls_ssl_cookie_ctx *ctx, unsigned long delay)
{
	ctx->timeout = delay;
}

void mbedtls_ssl_cookie_free(mbedtls_ssl_cookie_ctx *ctx)
{
	mbedtls_md_free(&ctx->hmac_ctx);

#if defined(MBEDTLS_THREADING_C)
	mbedtls_mutex_init(&ctx->mutex);
#endif

	mbedtls_zeroize(ctx, sizeof(mbedtls_ssl_cookie_ctx));
}

int mbedtls_ssl_cookie_setup(mbedtls_ssl_cookie_ctx *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
	int ret;
	unsigned char key[COOKIE_MD_OUTLEN];

	if ((ret = f_rng(p_rng, key, sizeof(key))) != 0) {
		return (ret);
	}

	ret = mbedtls_md_setup(&ctx->hmac_ctx, mbedtls_md_info_from_type(COOKIE_MD), 1);
	if (ret != 0) {
		return (ret);
	}

	ret = mbedtls_md_hmac_starts(&ctx->hmac_ctx, key, sizeof(key));
	if (ret != 0) {
		return (ret);
	}

	mbedtls_zeroize(key, sizeof(key));

	return (0);
}

/*
 * Generate the HMAC part of a cookie
 */
static int ssl_cookie_hmac(mbedtls_md_context_t *hmac_ctx, const unsigned char time[4], unsigned char **p, unsigned char *end, const unsigned char *cli_id, size_t cli_id_len)
{
	unsigned char hmac_out[COOKIE_MD_OUTLEN];

	if ((size_t)(end - *p) < COOKIE_HMAC_LEN) {
		return (MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL);
	}

	if (mbedtls_md_hmac_reset(hmac_ctx) != 0 || mbedtls_md_hmac_update(hmac_ctx, time, 4) != 0 || mbedtls_md_hmac_update(hmac_ctx, cli_id, cli_id_len) != 0 || mbedtls_md_hmac_finish(hmac_ctx, hmac_out) != 0) {
		return (MBEDTLS_ERR_SSL_INTERNAL_ERROR);
	}

	memcpy(*p, hmac_out, COOKIE_HMAC_LEN);
	*p += COOKIE_HMAC_LEN;

	return (0);
}

/*
 * Generate cookie for DTLS ClientHello verification
 */
int mbedtls_ssl_cookie_write(void *p_ctx, unsigned char **p, unsigned char *end, const unsigned char *cli_id, size_t cli_id_len)
{
	int ret;
	mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
	unsigned long t;

	if (ctx == NULL || cli_id == NULL) {
		return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);
	}

	if ((size_t)(end - *p) < COOKIE_LEN) {
		return (MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL);
	}
#if defined(MBEDTLS_HAVE_TIME)
	t = (unsigned long)mbedtls_time(NULL);
#else
	t = ctx->serial++;
#endif

	(*p)[0] = (unsigned char)(t >> 24);
	(*p)[1] = (unsigned char)(t >> 16);
	(*p)[2] = (unsigned char)(t >> 8);
	(*p)[3] = (unsigned char)(t);
	*p += 4;

#if defined(MBEDTLS_THREADING_C)
	if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
		return (MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret);
	}
#endif

	ret = ssl_cookie_hmac(&ctx->hmac_ctx, *p - 4, p, end, cli_id, cli_id_len);

#if defined(MBEDTLS_THREADING_C)
	if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
		return (MBEDTLS_ERR_SSL_INTERNAL_ERROR + MBEDTLS_ERR_THREADING_MUTEX_ERROR);
	}
#endif

	return (ret);
}

/*
 * Check a cookie
 */
int mbedtls_ssl_cookie_check(void *p_ctx, const unsigned char *cookie, size_t cookie_len, const unsigned char *cli_id, size_t cli_id_len)
{
	unsigned char ref_hmac[COOKIE_HMAC_LEN];
	int ret = 0;
	unsigned char *p = ref_hmac;
	mbedtls_ssl_cookie_ctx *ctx = (mbedtls_ssl_cookie_ctx *) p_ctx;
	unsigned long cur_time, cookie_time;

	if (ctx == NULL || cli_id == NULL) {
		return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);
	}

	if (cookie_len != COOKIE_LEN) {
		return (-1);
	}
#if defined(MBEDTLS_THREADING_C)
	if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
		return (MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret);
	}
#endif

	if (ssl_cookie_hmac(&ctx->hmac_ctx, cookie, &p, p + sizeof(ref_hmac), cli_id, cli_id_len) != 0) {
		ret = -1;
	}
#if defined(MBEDTLS_THREADING_C)
	if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
		return (MBEDTLS_ERR_SSL_INTERNAL_ERROR + MBEDTLS_ERR_THREADING_MUTEX_ERROR);
	}
#endif

	if (ret != 0) {
		return (ret);
	}

	if (mbedtls_ssl_safer_memcmp(cookie + 4, ref_hmac, sizeof(ref_hmac)) != 0) {
		return (-1);
	}
#if defined(MBEDTLS_HAVE_TIME)
	cur_time = (unsigned long)mbedtls_time(NULL);
#else
	cur_time = ctx->serial;
#endif

	cookie_time = ((unsigned long)cookie[0] << 24) | ((unsigned long)cookie[1] << 16) | ((unsigned long)cookie[2] << 8) | ((unsigned long)cookie[3]);

	if (ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout) {
		return (-1);
	}

	return (0);
}
#endif							/* MBEDTLS_SSL_COOKIE_C */
